U.S. patent number 4,687,813 [Application Number 06/817,757] was granted by the patent office on 1987-08-18 for production of coatings.
This patent grant is currently assigned to BASF Aktiengesellschaft. Invention is credited to Werner Lenz, Dieter Moeller, Hans Sander.
United States Patent |
4,687,813 |
Lenz , et al. |
August 18, 1987 |
**Please see images for:
( Certificate of Correction ) ** |
Production of coatings
Abstract
A process for the production of coatings based on reaction
products of (A) polyhydroxypolyacrylate resins obtained from
hydroxyalkyl esters of acrylic acid and/or methacrylic acid, alkyl
esters of acrylic acid and/or methacrylic acid, and one or more
polymerizable, olefinically unsaturated nitrogen-containing
heterocyclic compounds, with or without vinylaromatics,
(meth)acrylamides and other monomers, with (B)
isocyanurate-containing polyisocyanates which may or may not
contain biuret groups, have a functionality of from 2.5 to 6 and
consist of a mixture of polyisocyanates possessing predominantly
cycloaliphatically bonded isocyanate groups with those possessing
predominantly aliphatically bonded isocyanate groups. The process
is particularly useful for coating metal components.
Inventors: |
Lenz; Werner (Bad Duerkheim,
DE), Sander; Hans (Ludwigshafen, DE),
Moeller; Dieter (Ascheberg, DE) |
Assignee: |
BASF Aktiengesellschaft
(Ludwigshafen, DE)
|
Family
ID: |
6202330 |
Appl.
No.: |
06/817,757 |
Filed: |
January 6, 1986 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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624292 |
Jun 25, 1984 |
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Foreign Application Priority Data
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Jun 24, 1983 [DE] |
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3322829 |
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Current U.S.
Class: |
525/131; 525/124;
525/265; 525/123; 525/258 |
Current CPC
Class: |
C08G
18/721 (20130101); C08G 18/6229 (20130101); C08G
18/792 (20130101); C08G 18/6283 (20130101); C09D
133/14 (20130101); C09D 133/14 (20130101); C08L
2666/28 (20130101) |
Current International
Class: |
C08G
18/79 (20060101); C08G 18/62 (20060101); C08G
18/00 (20060101); C08G 18/72 (20060101); C09D
133/14 (20060101); C08F 008/30 () |
Field of
Search: |
;525/123,124,258,265,131 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1044932 |
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Feb 1965 |
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GB |
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1216479 |
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Dec 1967 |
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GB |
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1391066 |
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Jul 1971 |
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GB |
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Primary Examiner: Jacobs; Lewis T.
Assistant Examiner: Carrillo; A. L.
Attorney, Agent or Firm: Keil & Weinkauf
Parent Case Text
This application is a continuation of application Ser. No. 624,292,
filed on June 25, 1984, now abandoned.
Claims
We cIaim:
1. A process for the production of a coating based on a reaction
product of
(A) a polyhydroxypolyacrylate resin obtained from an ester of
acrylic acid or methacrylic acid with a monofunctional aliphatic
alcohol, or a mixture of esters of acrylic acid and methacrylic
acid with monofunctional aliphatic alcohols, a monoester of acrylic
acid with methacrylic acid with a polyfunctional aliphatic alcohol,
or a mixture of monoesters of acrylic acid and methacrylic acid
with polyfunctional aliphatic alcohols, and other copolymerizable
oefinically unsatured monomers, with
(B) a polyisocyanate which is unblocked or partially or completely
blocked with CH--, NH-- or OH-acidic blocking agents, contains
isocyanurate groups and may or may not contain biuret groups and
has a functionality of from 2.5 to 6,
wherein the polyhydroxypolyacrylate resin (A) used comprises
hydroxyl-containing copolymers consisting of
(a) from 6 to 70% by weight of one or more esters of the formula
##STR12## where R is hydrogen or methyl and R' is a straight-chain
or branched alkylene radieal of 2 to 18 carbon atoms or alkylene of
7 to 17 carbon atoms which contains one, two or three
cycloaliphatic groups, and some or all of the HO--R'--groups can be
replaced by Z--O--R'--groups, where Z is a radical of the general
formula ##STR13## where n is an integer from 1 to 3 and R" is an
alkylene chain of 4 to 8 carbon atoms which may additionally
contain 1 to 3 alkyl substituents with a total of not more than 10
carbon atoms and/or a cycloaliphatic radical of 6 to 10 carbon
atoms and/or an unsubstituted or alkyl-substituted aromatic radical
of 6 to 8 carbon atoms and/or an araliphatic radical of 7 to 9
carbon atoms and/or an alkoxy radical of 1 to 8 carbon atoms,
(b) from 0 to 50% by weight of one or more hydroxylalkyl esters of
acrylic acid or methacrylic acid of the formula ##STR14## where R
is hydrogen or methyl and R'" is the alkyl radical of a branched
aliphatic carboxylic acid of 4 to 26 carbon atoms,
(c) from 10 to 50% by weight of one or more alkyl esters of acrylic
acid or methacrylic acid, which form homopolymers having a glass
transition temperature of from +5.degree. to +120.degree. C.,
(d) from 0 to 10% by weight of a vinylaromatic,
(e) from 10 to 60% by weight of one or more alkyl esters or
alkylglycol esters of acrylic acid of methacrylic acid, which form
homopolymers which have a glass transistion temperature of from -80
to +4.5.degree. C., the alkylglycol esters containing not more than
2 ether oxygen bridges,
(f) from 0 to 10% by weight of an acrylamide or a methacrylamide
which may or may not be substituted at the amide nitrogen by one or
two alkyl radicals of 1 to 8 carbon atoms which may or may not
contain a carbonyl group, or by one or two phenyl radicals,
(g) from 1 to 25% by weight of one or more N-vinyl-imidazoles of
the formula ##STR15## where R.sup.1, R.sup.2, and R.sup.3 are each
hydrogen, methyl, ethyl, a straight-chain or branched alkyl radical
of 3 or 4 carbon atoms, or phenyl,
(h) from 0 to 20% by weight of monomers which are not stated under
(a) to (g) and whose copolymerized radicals ar inert to isocyanate
groups, with the proviso that the sum of the percentages stated
under (a) and (b) is from 6 to 70, the sum of the percentages
stated under (c), (d) and (g) is from 11 to 60, and the sum of the
percentages of the components stated under (a) to (h) is 100, and
the polyisocyanate (B) used, which contains isocyanurate groups,
may or may not contain biuret groups and has a functionality of
from 2.5 to 6, comprises a mixture of (B1) from 60 to 99% by weight
of an isocyanurate-containing polyisocyanate which possesses
predominantly cycloaliphatically bonded isocyanate groups, and (B2)
from 1 to 40% by weight of a polyisocyanate which contains biuret
or isocyanurate groups or both biuret and isocyanurate groups and
possesses predominantly aliphatically bonded isocyanate groups, the
sum of the percentages stated under (B1) and (B2) being 100, and/or
an isocyanurate-containing polyisocyanate which contains, as
copolymerized units,
(1) from 60 to 99% by weight of a diisocyanate possessing one or
more cycloaliphatically bonded isocyanate groups, and
(2) from 1 to 40% by weight of an aliphatic diisocyanate, the sum
of the percentages stated under (1) and (2) being 100.
2. A process as defined in claim 1, wherein the cycloaliphatic
isocyanurate-containing polyisocyanate (B1) used is a product
obtained from 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl
isocyanate (isophorone diisocyanate) as the diisocyanate
monomer.
3. A process as defined in claim 1, wherein a product obtained from
hexamethylene diisocyanate, as the diisocyanate monomer, is used as
the polyisocyanate (B2) which contains biuret groups and possesses
predominantly aliphatically bonded isocyanate groups.
4. A process as defined in claim 1, wherein from 2 to 30% by weight
of the biuret-containing polyisocyanate based on hexamethylene
diisocyanate is used as component (B2).
5. A process as defined in claim 1, wherein a product obtained from
hexamethylene diisocyanate, as the diisocyanate monomer, is used as
the isocyanurate-containing polyisocyanate (B2) possessing
predominantly aliphatically bonded isocyanate groups.
6. A process as defined in claim 1, wherein from 2 to 30% by weight
of the isocyanurate-containing polyisocyanate based on
hexamethylene diisocyanate is used as component (B2).
7. A process as defined in claim 1, wherein a product which
contains, as copolymerized units, (1) from 60 to 99% by weight of
isophorone diisocyanate and (2) from 1 to 40% by weight of
hexamethylene diisocyanate is used as the isocyanurate-containing
polyisocyanate (B) possessing predominantly cycloaliphatically
bonded isocyanate groups, with the proviso that the sum of the
percentages stated under (1) and (2) is 100.
8. A process as defined in claim 7, wherein the polyisocyanate used
contains, as copolymerized units, (1) from 70 to 98% by weight of
isophorone diisocyanate and (2) from 2 to 30% by weight of
hexamethylene diisocyanate, with the proviso that the sum of the
percentages stated under (1) and (2) is 100.
9. A process as defined in claim 1, wherein the hydroxyl number of
the hydroxyl-containing copolymer (A) is from 30 to 250.
10. A process as defined in claim 1, wherein the hydroxyl number of
the hydroxyl-containing copolymer (A) is from 50 to 150.
11. A process as defined in claim 1, wherein hydroxyethyl acrylate,
hydroxyethyl methacrylate, 2-hydroxypropyl acrylate or
2-hydroxypropyl methacrylate, or a mixture of these compounds, is
used as component (a) of the hydroxyl-containing copolymer.
12. A process as defined in claim 1 wherein butane-1,4-diol
monoacrylate, butane-1,4-diol monomethacrylate, hexane-1,6-diol
monoacrylate or hexane-1,6-diol monomethacrylate, or a mixture of
these compounds, is used as component (a) of the
hydroxyl-containing copolymer.
13. A process as defined in claim 1, wherein component (a) of the
hydroxyl-containing copolymer is a reaction product of one or more
compounds from the group consisting of hydroxyethyl acrylate,
hydroxyethyl methacrylate, 2-hydroxypropyl acrylate,
2-hydroxypropyl methacrylate, butane-1,4-diol monoacrylate,
butane-1,4-diol monomethacrylate, hexane-1,6-diol monoacrylate and
hexane-1,6-diol monomethacrylate with .epsilon.-caprolactone which
is unsubstituted or substituted by 1 to 3alkyl radicals possessing
a total of not more than 10 carbon atoms, the reactants being used
in a molar ratio of from 1.5:1 to 1:3.
14. A process as defined in claim 13, wherein component (a) of the
hydroxyl-containing copolymer is a reaction product of one or more
compounds of the group consisting of hydroxyethyl acrylate,
hydroxyethyl methacrylate, 2-hydroxypropyl acrylate,
2-hydroxypropyl methacrylate, butane-1,4-diol monoacrylate and
butane-1,4-diol monomethacrylate with .epsilon.-caprolactone, the
reactants being used in a molar ratio of from 1.5:1 to 1:3.
15. A process as defined in claim 1, wherein a mixture of from 1 to
99% by weight of the reaction products stated in claim 13 with from
99 to 1% by weight of hydroxyethyl acrylate, hydroxyethyl
methacrylate, butane-1,4-diol monoacrylate, butane-1,4-diol
monomethacrylate or a mixture of these compounds is used as
component (a) of the hydroxyl-containing copolymer.
16. A process as defined in claim 1, wherein from 2 to 20% by
weight of component (g) is used for the hydroxyl-containing
copolymer.
17. A process as defined in claim 1, wherein the ratio of the
reactants (A) and (B) is chosen so that the ratio of the number of
equivalents of isocyanate groups which are unblocked or partially
or completely blocked with CH--, NH--or OH--acidic blocking agents
to the number of equivalents of reactive hydroxyl groups is from
0.25:1 to 4:1.
18. A process as defined in claim 1, wherein a monofunctional
ketoxime is used as the blocking agent for the partially or
completely blocked polyisocyanate.
19. A process as defined in claim 1, wherein dimethyl ketoxime or
methyl ethyl ketoxime is used as the blocking agent for the
polyisocyanate.
20. A process as defined in claim 1, wherein a mixture of from 1 to
99% by weight of the reaction products stated in claim 14 with from
99 to 1% by weight of hydroxyethyl acrylate, hydroxyethyl
methacrylate, butane-1,4-diol monoacrylate, butane-1,4-diol
monomethyacrylate or a mixture of these compounds is used as
component (a) of the hydroxyl-containing copolymer.
Description
The present invention relates to a process for the production of
coatings using coating agents which contain, as binders, reaction
products of selected polyhydroxypolyacrylate resins with
polyisocyanates which contain isocyanurate groups and may contain
biuret groups, may be partially or completely blocked with CH--,
NH-- or OH--acidic blocking agents, have a functionality of from
2.5 to 6 and contain isocyanate groups which are predominantly
cycloaliphatically bonded but some of which are aliphatically
bonded.
German Laid-Open application No. DOS 1,720,265 describes a process
for the preparation of light-stable coatings based on reaction
products of polyhydroxypolyacrylate resins prepared by
copolymerization of monoesters of an acrylic acid and/or
methacrylic acid with polyfunctional aliphatic alcohols, esters of
acrylic acid and/or methacrylic acid with monofunctional aliphatic
alcohols and/or other copolymerizable olefinically unsaturated
monomers in organic solution. The binder combinations described
here, consisting of hydroxyl-containing acrylic resins and a
biuretized triisocyanate give highly glossy flexible pigmented
surface-coating films which possess excellent stability to weather
and harden rapidly at low temperatures, the resulting film being
scratch-resistant. However, a disadvantage of these surface coating
mixtures is that the biuretized triisocyanates used have a tendency
to decompose once again into the parent diisocyanate monomers and
moreover have a pronounced toxicity when inhaled in the form of
spray mists, so that these triisocyanates are unacceptable from the
point of view of industrial hygiene.
German Published Application DAS 1,669,008 discloses that a mixture
of a hydroxyl-containing copolymer based on methyl methacrylate,
vinyl aromatics, monoacrylates and/or monomethacrylates of
alkanols, other copolymerizable olefinically unsaturated monomers,
monomers containing one or more hydroxyl groups in the molecule and
a monomer containing tertiary amino groups with one or more
polyisocyanates in organic solution can be used as a surface
coating. These surface coating mixtures give hard,
scratch-resistant, tough films which are stable to weather, exhibit
good adhesion, are resistant to water, solvents and chemicals and
possess high gloss. The hardeners listed in this case include
aromatic and aliphatic polyisocyanates which contain urethane,
isocyanurate and biuret groups. However, there is no mention of
isocyanurate-containing polyisocyanates which are substantially
acceptable from the point of view of industrial hygiene and contain
predominantly cycloaliphatically bonded isocyanate groups. Monomers
containing tertiary amino groups which are mentioned are those
possessing highly basic aliphatic tertiary amino groups. Although
this accelerates the reaction between the polyisocyanate and the
polyol, the surface coating film must be expected to have
relatively low resistance to acids and a strong tendency to yellow
on weathering.
German Published applications Nos. DAS 1,668,510, DAS 2,054,239,
DAS 2,603,259, DAS 2,626,900 and DAS 2,659,853 and German Laid-Open
application Nos. DOS 2,460,329 and DOS 2,851,613 likewise describe
processes for the preparation of organic solutions of
hydroxyl-containing copolymers, and for the production of coatings
from binders based on these copolymers in combination with
aliphatic biuretized triisocyanates. For the stated copolymers,
suitable hydroxyl-containing acrylate monomers are reaction
products of acrylic acid and/or methacrylic acid with a glycidyl
ester of a branched aliphatic carboxylic acid of 4 to 26 carbon
atoms and, if appropriate, hydroxyalkyl acrylates or methacrylates
where alkyl is of 2 to 4 carbon atoms, and suitable comonomers are
esters of acrylic acid and/or methacrylic acid with alkanols of 1
to 12 carbon atoms and styrene or alkylstyrene. The introduction of
side hydroxyl groups via the glycidyl ester is effected by
incorporating acrylic acid and/or methacrylic acid as copolymerized
units and at the same time esterifying the carboxyl groups with the
glycidyl compound.
These binder combinations, too, can be used to produce highly
glossy, rapidly curing, scratch-resistant, water-resistant,
flexible surface coating films which are very stable to weather.
However, the disadvantage once again is the fact that in this case
too the above biuretized triisocyanates are used, which are not
completely acceptable from the point of view of industrial
hygiene.
German Laid-Open application No. DOS 2,836,612 describes a process
for the production of coatings based on binders consisting of
surface coating polyisocyanates which contain biuret, urethane or
isocyanurate groups and hydroxyl-containing acrylate copolymers
obtained from hydroxyalkyl acrylates or methacrylates where
hydroxyalkyl is of 2 to 4 carbon atoms, and substituted or
unsubstituted styrene and/or methyl methacrylate, esters of acrylic
acid and/or methacrylic acid with alcohols of 1 to 12 carbon atoms,
mono- or dicarboxylic acids which may or may not be .alpha.,
.beta.-monoolefinically unsaturated and acrylonitrile and/or
methacrylonitrile. The particular advantages of this process are
that these binder combinations give clear, highly compatible
surface coating mixtures as well as glossy, rapidly drying, hard
and sufficiently flexible surface coating films. In order to
realize these advantageous performance characteristics, especially
the good compatibility with isocyanurate-containing
polyisocyanates, it is absolutely necessary to use from 5 to 30% by
weight of acrylonitrile and/or methacrylonitrile as comonomers in
the hydroxyl-containing acrylic resin. However, the use of such
nitrile-containing copolymers in two-component polyurethane surface
coatings leads to substantial yellowing on prolonged thermal
loading, and to chalking of the pigmented surface coating film on
weathering. The description also states that, as one of the
preferred surface coating polyisocyanates, it is possible to use,
inter alia, an isocyanurate-containing polyisocyanate based on
IPDI, ie. containing predominantly cycloaliphatically bonded
isocyanate groups, in combination with the acrylic resins. However,
such binder combinations are not described in the Examples, nor
does the description of German Laid-Open application No. DOS
2,836,612 give any indication of the flexibility, the increase in
hardness as a function of time, and in particular the resistance of
the surface coating films to premium grade gasoline after a certain
curing time, the latter property being extremely important with
regard to the use of the surface coatings for automotive
repair.
German Laid-Open application No. DOS 2,900,592 describes reaction
products of glycidyl-containing acrylic resins and
hydroxyl-containing secondary monoamines, the acrylic resins being
random copolymers of glycidyl acrylate and/or methacrylate,
vinylaromatics, methyl methacrylate, acrylonitrile,
methacrylonitrile, esters of acrylic acid with alcohols of 1 to 12
carbon atoms and/or esters of methacrylic acid with alcohols of 2
to 12 carbon atoms, with or without hydroxyalkyl acrylates and/or
methacrylates where hydroxyalkyl is of 2 to 4 carbon atoms and
mono- and/ or dicarboxylic acids which may or may not be .alpha.,
.beta.-monoolefinically unsaturated, and are used as crosslinking
components in combination with polyisocyanates which can also
possess isocyanurate groups. Thus, the acrylic resin component
claimed in this application inevitably contains tertiary amino
groups, in addition to predominantly secondary hydroxyl groups, as
functional groups. In addition to the good compatibility of these
binder combinations with aromatic solvents, the pot lives, which
are surprisingly long in spite of the presence of tertiary amino
groups, are especially noteworthy. As will readily be apparent to
one skilled in the art, these long pot lives of the surface coating
mixtures are attributable in particular to the fact that the
acrylic resins virtually exclusively contain secondary hydroxyl
functions as reactive groups. Hence, it is also in no way
surprising that the corresponding reaction product which is
described in the Comparative Example, is based on diethanolamine
and contains primary hydroxyl groups gives an excessively short pot
life with polyisocyanates compared with the copolymers described in
this laid-open application. In the process described, it is
therefore not possible to obtain acrylic resins which can be
readily used for two-component polyurethane surface coatings and
contain large amounts of primary hydroxyl groups in addition to
tertiary amino groups. Moreover, binders which contain strongly
basic amino-containing copolymers have the disadvantages that their
acid-resistance --which is absolutely necessary, for example, for
topcoats for automotive repair--is relatively low, and that,
compared with amino-free systems, they exhibit pronounced yellowing
on prolonged weathering.
German Laid-Open application No. DOS 3,010,719 relates to a process
for the production of metallic effect coatings having improved
weather-resistance, in which the topcoats used are clear finishes
whose binders essentially contain, as the polyol component,
inevitably polyesterols which have a low aromatics content and, if
appropriate, polyacrylate-polyols, and contain, as the
polyisocyanate component, adducts which contain biuret groups
and/or isocyanurate groups and possess aliphatic isocyanate groups
which may or may not be blocked. The clear finishes described in
this application possess, in particular, high crack resistance on
weathering. However, the description states that the mixtures are
preferably used when the surface coating is cured with the action
of heat, since these conditions result in homogeneous clear surface
coating films (cf. Example 6; baking temperature: 80.degree. C.).
However, surface coatings which are particularly suitable for the
automotive repair sector must also be capable of being cured
without difficulty at room temperature and give homogeneous
coatings in this case. A further general disadvantage of the
combinations, described in this application, of polyester polyols
having a low aromatics content with polyisocyanates is the fact
that such systems exhibit relatively slow surface drying and
thorough drying at room temperature in comparison with the
polyacrylatepolyol/polyisocyanate combinations, which dry rapidly
and are then resistant to premium grade gasoline. Accordingly, the
surface coating mixtures described in the Examples of German
Laid-Open application No. DOS 3,010,719 all harden only at
80.degree. C., ie. at elevated temperature.
German Laid-Open application No. DOS 3,027,776 relates to a process
for the preparation of hydroxyl-containing (meth)acrylic resins
which are modified with .delta.-caprolactone and can be crosslinked
with polyisocyanates. These copolymers, even when combined with an
isocyanurate-containing polyisocyanate based on isophorone
diisocyanate and containing predominantly cycloaliphatically bonded
isocyanate groups, give hard, weather-resistant, flexible coatings
which exhibit good adhesion to metal and are resistant to water and
to chemicals. However, the systems described have the disadvantage
that they have to be baked at elevated temperatures (from 110 to
150.degree. C.) if cycloaliphatic polyisocyanates are used, ie.
they are unsuitable for surface coatings for automotive repair.
German Laid-Open application No. DOS 3,137,133 relates to a process
for the production of coatings by reacting
polyhydroxypoly(meth)acrylate resins, prepared from hydroxyalkyl
acrylates or methacrylates which have primary hydroxyl groups and
in which the alkylene main chain is of 4 to 10 carbon atoms and
special acrylates or methacrylates as comonomers, with
isocyanurate-containing polyisocyanates which possess predominantly
cycloaliphatically bonded isocyanate groups. As a result of the use
of the special polyisocyanates, the surface coatings obtained from
the stated components have very low toxicity when inhaled and give
non-yellowing, acid-resistant coatings which are very useful as
topcoats for automotive repair, are cured at low temperatures and
possess high flexibility, scratch-resistance, final hardness and
stability to weather. The rate at which these surface coating films
are cured at room temperature, and their resistance to premium
grade gasoline, satisfy practical requirements, but in some cases
do not quite reach the standard of the most advantageous prior art
binder systems, for example those based on hydroxyl-containing
polyacrylate resins and biuret-containing aliphatic
polyisocyanates.
In contrast to the biuretized aliphatic polyisocyanates preferably
used to date in topcoats for automotive repair,
isocyanurate-containing polyisocyanates possessing predominantly
cycloaliphatically bonded isocyanate groups, preferably products
prepared by trimerization of
3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate
(=isophorone diisocyanate) in accordance with British Patent
1,391,066 and German Laid-Open applications Nos. DOS 2,325,826 and
DOS 2,732,662, possess extremely low toxicity when inhaled, even in
the form of aerosols; this is very advantageous with regard to
their use as surface coatings for automotive repair.
Combinations of cycloaliphatic isocyanurate-containing
polyisocyanates and minor amounts of polyisocyanates which contain
biuret and/or isocyanurate groups and possess aliphatically bonded
isocyanate groups, preferably compounds based on hexamethylene
diisocyanate, are substantially more advantageous than, for
example, pure biuretized aliphatic polyisocyanates in terms of
their industrial hygiene properties. The same also applies to, for
example, the polyisocyanates described in German Laid-Open
application No. DOS 3,033,860, which are prepared by trimerization
of a mixture of 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl
isocyanate with a minor amount of hexamethylene diisocyanate. In
combination with suitable polyols, all of the stated
polyisocyanates give surface coating films which are very stable to
weather and have a low tendency to yellow.
If the prior art hydroxyl-containing polyacrylate resins, as
described in, for example, the above German Published applications
Nos. DAS 1,669,008, DAS 1,668,510, DAS 2,054,239, DAS 2,603,259,
DAS 2,626,900 and DAS 2,659,853 and German Laid-Open applications
Nos. DOS 2,460,329 and DOS 2,851,613, ie. those based on
hydroxyalkyl acrylates and/or methacrylates where the main chain of
the alcohol radical is of 2 or 3 carbon atoms, with or without
adducts of glycidyl esters of a branched aliphatic monocarboxylic
acid with acrylic acid and/or methacrylic acid, are combined with
these isocyanurate-containing polyisocyanates which contain
predominantly cycloaliphatically bonded isocyanate groups and may
or may not furthermore contain biuret groups, the surface coating
films obtained within curing times which are conventional in
practice and at any curing temperature conventionally employed for
coating in automotive repair, ie. from room temperature to
80.degree. C., possess inadequate mechanical properties and in some
cases insufficient resistance to premium grade gasoline. If acryljc
resins having a high hydroxyl number (>100) and predominantly
consisting of monomers which give homopolymers having a high glass
transition temperature (>20.degree. C.) are used, the surface
coating films obtained under curing conditions conventionally used
in practice (about 7 days at room temperature or not more than
30-60 minutes at 80.degree. C.) have adequate scratch-resistance
and in some cases sufficient resistance to gasoline but are much
too brittle, ie. they do not satisfy practical requirements. The
use of acrylic resins which have a lower hydroxyl number (<100)
and contain large amounts of monomer units which give homopolymers
having a low glass transition temperature (<5.degree. C.)
accordingly results in surface coating films which possess adequate
flexibility but whose scratch-resistance and resistance to premium
grade gasoline are too low to satisfy practical requirements.
Although the use of larger amounts of catalyst results in some
cases in films having improved flexibility as well as improved
scratch-resistance, these films do not harden rapidly enough to
give gasoline-resistant coatings. Moreover, the pot lives of the
corresponding surface coating mixtures are too short.
Like the above combinations, two-component surface coatings
consisting of the polyhydroxypolyacrylate resins described in
German Laid-Open application No. DOS 1,720,265 and
isocyanurate-containing polyisocyanates which contain predominantly
cycloaliphatically bonded isocyanate groups and may or may not
contain biuret groups give films which have inadequate flexibility.
If the polyhydroxypolyacrylates described in German Laid-Open
application No. DOS 2,836,612, which inevitably contain nitrile
side groups, are combined with the above polyisocyanates, the
resulting surface coating films are, as stated above, useless as
topcoats for automotive repair and have an excessive tendency to
yellow and insufficient stability to weather. In combination with
these polyisocyanates, the acrylic resins claimed in German
Laid-Open application No. DOS 2,900,592, which inevitably possess
both hydroxyl and tertiary amino groups, present problems in that
the surface coating films have insufficient resistance to acids, as
stated above.
The combinations, described in German Laid-Open applications Nos.
DOS 3,010,719 and DOS 3,027,776, of polyester polyols,
hydroxyl-containing acrylic resins or
.epsilon.-caprolactone-modified hydroxyl-containing
poly(meth)acrylates on the one hand and predominantly
cycloaliphatic polyisocyanates on the other hand are, as stated
above, not very useful as topcoats for automotive repair,
particularly because of the relatively high baking temperatures
required and the slow surface drying.
The binders described in German Laid-Open application No. DOS
3,137,133, which consist of special hydroxylcontaining
polyacrylates and isocyanurate-containing polyisocyanates
possessing predominantly cycloaliphatically bonded isocyanate
groups, are very useful as such for the automotive repair sector.
However, somewhat faster curing of the surface coating films at
room temperature as well as improved resistance to premium grade
gasoline are desirable.
It is an object of the present invention to provide a novel process
for the production of coatings, in which binders based on
polyisocyanates which contain isocyanurate groups and may or may
not contain biuret groups, have a functionality of from 2.5 to 6,
preferably from 3 to 5, and possess predominantly
cycloaliphatically bonded isocyanate groups, and
hydroxyl-containing polyacrylate resins, are employed in organic
solution, these binders being free of the stated technical
disadvantages. Thus, using the novel process, starting from surface
coating mixtures which have a sufficiently long pot life and
carrying out the procedure at low temperatures and without the
addition of a catalyst result in non-yellowing films which harden
very rapidly to give coatings which are resistant to premium grade
gasoline and possess high flexibility, scratch-resistance and
weather-resistance or resistance to chalking.
For the purposes of the present invention, functionality is defined
as the average number of reactive isocyanate groups, blocked or
unblocked, per polyisocyanate molecule.
We have found, surprisingly, that this object is achieved by
coatings based on a reaction product of unblocked or partially or
completely blocked, preferably unblocked, polyisocyanates which
contain isocyanurate groups and may or may not contain biuret
groups, have a functionality of from 2.5 to 6, preferably from 3 to
5, and possess predominantly cycloaliphatically bonded isocyanate
groups, with hydroxyl-containing polyacrylates of specific
composition.
The present invention relates to a process for the production of
coatings based on a reaction product of
(A) a polyhydroxypolyacrylate resin obtained from esters of acrylic
acid and/or methacrylic acid with monofunctional aliphatic
alcohols, monoesters of acrylic acid and/or methacrylic acid with
polyfunctional aliphatic alcohols and other copolymerizable
olefinically unsaturated monomers with
(B) a polyisocyanate which is unblocked or partially or completely
blocked with CH--, NH-- or OH--acidic blocking agents, contains
isocyanurate groups and may or may not contain biuret groups and
has a functionality of from 2.5 to 6,
wherein the polyhydroxypolyacrylate resin (A) used comprises
hydroxyl-containing copolymers consisting of
(a) from 6 to 70 % by weight of one or more esters of the general
formula ##STR1## where R is hydrogen or methyl and R' is a
straight-chain or branched alkylene radical of 2 to 18 carbon atoms
or alkylene of 7 to 17 carbon atoms which contains one, two or
three cycloaliphatic groups, and some or all of the HO--R'--groups
can be replaced by Z--O--R'--groups, where Z is a radical of the
general formula ##STR2## where n is an integer from 1 to 3 and R"
is an alkylene chain of 4 to 8 carbon atoms which may additionally
contain 1 to 3 alkyl substituents with a total of not more than 10
carbon atoms and/or a cycloaliphatic radical of 6 to 10 carbon
atoms and/or an unsubstituted or alkyl-substituted aromatic radical
of 6 to 8 carbon atoms and/or an araliphatic radical of 7 to 9
carbon atoms and/or an alkoxy radical of 1 to 8 carbon atoms,
(b) from 0 to 50 % by weight of one or more hydroxyalkyl esters of
acrylic acid and/or methacrylic acid of the general formula
##STR3## where R is hydrogen or methyl and R'" is the alkyl radical
of a branched aliphatic carboxylic acid of 4 to 26 carbon
atoms,
(c) from 10 to 50 % by weight of one or more alkyl esters of
acrylic acid and/or methacrylic acid, which form homopolymers
having a glass transition temperature of from +5.degree. to
+120.degree. C.,
(d) from 0 to 10 % by weight of a vinylaromatic,
(e) from 10 to 60 % by weight of one or more alkyl esters and/or
alkylglycol esters of acrylic acid and/or methacrylic acid, which
form homopolymers which have a glass transition temperature of from
-80.degree. to +4.5.degree. C., the alkylglycol esters containing
not more than 2 ether oxygen bridges,
(f) from 0 to 10 % by weight of an acrylamide and/or a
methacrylamide which may or may not be substituted at the amide
nitrogen by one or two alkyl radicals of 1 to 8 carbon atoms which
may or may not contain a carbonyl group, or by one or two phenyl
radicals,
(g) from 1 to 25 % by weight of one or more polymerizable
olefinically unsaturated heterocyclic compounds of the general
formulae (I) to (VIII) ##STR4## where R is hydrogen or methyl,
R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are identical or different
and are each hydrogen, methyl, ethyl, a straight-chain or branched
alkyl radical of 3 or 4 carbon atoms, or phenyl which is
unsubstituted or substituted by alkyl of 1 to 4 carbon atoms,
halogen or nitro, or are each a group of the general formula
--R.sup.I --A--R.sup.II, where A is oxygen or sulfur, R.sup.I is
methylene or ethylene or is phenylene which is unsubstituted or
substituted by alkyl of 1 to 4 carbon atoms or by halogen or nitro
and R.sup.II is methyl or ethyl or is phenyl which is unsubstituted
or substituted by alkyl of 1 to 4 carbon atoms or by halogen or
nitro, or are each halogen or nitro, or a group of the general
formulae --OR.sup.III, --COOR.sup.III, --SO.sub.2 R.sup.III,
--CONR.sup.III R.sup.IV or --SO.sub.2 NR.sup.III R.sup.IV, where
R.sup. III and R.sup.IV are identical or different and are each
methyl, ethyl, a straight-chain or branched alkyl radical of 3 or 4
carbon atoms, or phenyl which is unsubstituted or substituted by
alkyl of 1 to 4 carbon atoms or by halogen or nitro, and
furthermore in the formulae (I), (II), (III), (V), (VI) and (VIII)
R.sup.2 and R.sup.3, or in the formula (III) R.sup.3 and R.sup.4,
or in the formulae (II) and (IV) R.sup.3 and R.sup.4 or R.sup.1 and
R.sup.2, or in the formulae (II) and (IV) R.sup.3 and R.sup.4 and
R.sup.1 and R.sup.2, together with the heterocyclic ring, can form
a fused aromatic six-membered ring which is unsubstituted or
substituted by alkyl of 1 to 4 carbon atoms or by halogen or nitro,
and
(h) from 0 to 20 % by weight of monomers which are not stated under
(a) to (g) and whose copolymerized radicals are inert to isocyanate
groups, with the proviso that the sum of the percentages stated
under (a) and (b) is from 6 to 70, the sum of the percentages
stated under (c), (d) and (g) is from 11 to 60, and the sum of the
percentages of the components stated under (a) to (h) is 100, and
the polyisocyanate (B) used, which contains isocyanurate groups,
may or may not contain biuret groups and has a functionality of
from 2.5 to 6, comprises a mixture of (B1) from 60 to 99 % by
weight of an isocyanurate-containing polyisocyanate which possesses
predominantly cycloaliphatically bonded isocyanate groups and (B2)
from 1 to 40% by weight of a polyisocyanate which contains biuret
and/or isocyanurate groups and possesses predominantly
aliphatically bonded isocyanate groups, the sum of the percentages
stated under (B1) and (B2) being 100, and/or an
isocyanurate-containing polyisocyanate which contains, as
copolymerized units,
(1) from 60 to 99% by weight of a diisocyanate possessing one or
more cycloaliphatically bonded isocyanate groups and
(2) from 1 to 40% by weight of an aliphatic diisocyanate, the sum
of the percentages stated under (1) and (2) being 100.
The present invention furthermore relates to metal components which
are provided with a coating by means of the novel process.
Regarding the reaction products used for the novel process, and
their components, the following may be stated specifically:
(A) suitable polyhydroxypolyacrylate resins (A) are
hydroxyl-containing copolymers comprising
(a) from 6 to 70 % by weight of one or more esters of the general
formula ##STR5## where R is hydrogen or methyl and R' is a
straight-chain or branched alkylene radical of 2 to 18 carbon atoms
or alkylene of 7 to 17 carbon atoms which contains one, two or
three cycloaliphatic groups, and some or all of the HO--R'--groups
can be replaced by Z--O--R'--groups, where Z is a radical of the
general formula ##STR6## where n is an integer from 1 to 3 and R"
is an alkylene chain of 4 to 8 carbon atoms which may additionally
contain 1 to 3 alkyl substituents with a total of not more than 10
carbon atoms and/or a cycloaliphatic radical of 6 to 10 carbon
atoms and/or an unsubstituted or alkylsubstituted aromatic radical
of 6 to 8 carbon atoms and/or an araliphatic radical of 7 to 9
carbon atoms and/or an alkoxy radical of 1 to 8 carbon atoms,
(b) from 0 to 50 % by weight of one or more hydroxyalkyl esters of
acrylic acid and/or methacrylic acid of the general formula
##STR7## where R is hydrogen or methyl and R'" is the alkyl radical
of a branched aliphatic carboxylic acid of 4 to 26 carbon
atoms,
(c) from 10 to 50 % by weight of one or more alkyl esters of
acrylic acid and/or methacrylic acid, which form homopolymers
having a glass transition temperature of from +5.degree. to
+120.degree. C.,
(d) from 0 to 10 % by weight of a vinylaromatic,
(e) from 10 to 60 % by weight of one or more alkyl esters and/or
alkylglycol esters of acrylic acid and/or methacrylic acid, which
form homopolymers which have a glass transition temperature of from
-80.degree. to +4.5.degree. C., the alkylglycol esters containing
not more than 2 ether oxygen bridges,
(f) from 0 to 10 % by weight of an acrylamide and/or a
methacrylamide which may or may not be substituted at the amide
nitrogen by one or two alkyl radicals of 1 to 8 carbon atoms which
may or may not contain a carbonyl group, or by one or two phenyl
radicals,
(g) from 1 to 25 % by weight of one or more polymerizable
olefinically unsaturated heterocyclic compounds of the general
formulae (I) to (VIII) ##STR8## where R is hydrogen or methyl,
R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are identical or different
and are each hydrogen, methyl, ethyl, a straight-chain or branched
alkyl radical of 3 or 4 carbon atoms, or phenyl which is
unsubstituted or substituted by alkyl of 1 to 4 carbon atoms,
halogen or nitro, or are each a group of the general formula
--R.sup.I --A--R.sup.II, where A is oxygen or sulfur, R.sup.I is
methylene or ethylene or is phenylene which is unsubstituted or
substituted by alkyl of 1 to 4 carbon atoms or by halogen or nitro
and R.sup.II is methyl or ethyl or is phenyl which is unsubstituted
or substituted by alkyl of 1 to 4 carbon atoms or by halogen or
nitro, or are each halogen or nitro, or a group of the general
formulae --OR.sup.III, --COOR.sup.III, --SO.sub.2 R.sup.III,
--CONR.sup.III R.sup.IV or --SO.sub.2 NR.sup.III R.sup.IV, where
R.sup. III and R.sup.IV are identical or different and are each
methyl, ethyl, a straight-chain or branched alkyl radical of 3 or 4
carbon atoms, or phenyl which is unsubstituted or substituted by
alkyl of 1 to 4 carbon atoms or by halogen or nitro, and
furthermore in the formulae (I), (II), (III), (V), (VI) and (VIII)
R.sup.2 and R.sup.3, or in the formula (III) R.sup.3 and R.sup.4,
or in the formulae (II) and (IV) R.sup.3 and R.sup.4 or R.sup.1 and
R.sup.2, or in the formulae (II) and (IV) R.sup.3 and R.sup.4 and
R.sup.1 and R.sup.2, together with the heterocyclic ring, can form
a fused aromatic six-membered ring which is unsubstituted or
substituted by alkyl of 1 to 4 carbon atoms or by halogen or
nitro,
(h) from 0 to 20 % by weight of monomers which are not stated under
(a) to (g) and whose copolymerized radicals are inert to isocyanate
groups, with the proviso that the sum of the percentages stated
under (a) and (b) is from 6 to 70, the sum of the percentages
stated under (c), (d) and (g) is from 10 to 60, and the sum of the
percentages of the components stated under (a) to (h) is 100.
(a) Examples of suitable esters of the general formula ##STR9##
where R is hydrogen or methyl and R' is a straight-chain or
branched alkylene radical of 2 to 18 carbon atoms or an alkylene
radical of 7 to 17 carbon atoms which contains one, two or three
cycloaliphatic groups, and some or all of the HO--R'--groups can be
replaced by Z--O--R'--groups, where Z is a radical of the general
formula ##STR10## where n is an integer from 1 to 3 and R" is an
alkylene chain of 4 to 8 carbon atoms which may additionally
contain 1 to 3 alkyl substituents with a total of not more than 10
carbon atoms and/or a cycloaliphatic radical of 6 to 10 carbon
atoms and/or an unsubstituted or alkyl-substituted aromatic radical
of 6 to 8 carbon atoms and/or an araliphatic radical of 7 to 9
carbon atoms and/or an alkoxy radical of 1 to 8 carbon atoms, are
monoesters of dihydric alcohols, such as decane-1.10-diol,
octane-1,8-diol, pentane-1,5-diol, 1,4-dihydroxymethylcyclohexane,
3(4),8(9)-dihydroxymethyltricyclo[5.2.1.0.sub.2.6 ]decane,
2,2-dimethylpropane -1,3-diol, butane-1,4-diol, hexane-1,6-diol,
propane-1,2-diol or ethane-1,2-diol, with acrylic acid or
methacrylic acid, eg. decane-1,10-diol monoacrylate,
decane-1,.10-diol monomethacrylate, octane-1,8-diol monoacrylate,
octane-1,8-diol monomethacrylate, pentane-1,5-diol monoacrylate,
pentane-1,5-diol monomethacrylate, 1,4-dihydroxymethylcyclohexane
monoacrylate, 1,4-dihydroxymethylcyclohexane monomethacrylate,
3(4),8(9)-dihydroxymethyltricyclo[5.2.1.0.sup.2.6 ]decane
monoacrylate and monomethacrylate, 2,2-dimethylpropane-1,3-diol
monoacrylate and monomethacrylate, butane-1,4-diol
monomethacrylate, hexane1,6-diol monomethacrylate, 2-hydroxypropyl
acrylate, 2-hydroxypropyl methacrylate and preferably hydroxyethyl
acrylate, hydroxyethyl methacrylate or butane-1,4-diol monoacrylate
and monomethacrylate and hexane-1,6-diol monoacrylate and
monomethacrylate.
Furthermore, products can be used which are obtained by reacting
the above hydroxyl-containing acrylates or methacrylates with
unsubstituted or substituted lactones having 4 to 8 carbon atoms in
the ring, the molar ratio of the reactants being from 1.5:1 to 1:3.
Examples of lactones which can be used for this purpose are:
.delta.-valerolactone, .gamma., .gamma.-dimethylvalerolactone,
.epsilon.-caprolactone , .alpha.-, .beta.-, .gamma.-, .delta.- and
.epsilon.-methyl-.epsilon.-caprolactone, the corresponding
monoethyl-, monopropyl-, monoisopropyl- and
monooctyl-.epsilon.-caprolactones, .beta., .delta.-dimethyl-,
.gamma., .gamma.-dimethyl-, .beta., .delta., .delta.-trimethyl-,
.beta.-methyl- .delta.-ethyl-, .gamma.-cyclohexyl- and
.gamma.-phenyl- .epsilon.-caprolactone, .rho.-enantholactone and
.delta.-caprylolactone, .delta.-caprolactone being particularly
preferred.
Preferred lactone adducts are the reaction products of hydroxyethyl
acrylate and/or methacrylate and/or -hydroxypropyl acrylate and/or
methacrylate and/or butane-1,4-diol monoacrylate and/or
hexane-1,6-diol monoacrylate and/or butane-1,4-diol
monomethacrylate and/or hexane-1,6-diol monomethacrylate with
.epsilon.-caprolactone in a molar ratio of from 1.5:1 to 1:3, the
adducts based on hydroxyethyl acrylate and/or methacrylate,
2-hydroxypropyl acrylate and/or methacrylate and butane-1,4-diol
monoacrylate and/or monomethacrylate being particularly preferred.
It is of course also possible to use, as the hydroxyl-containing
acrylates and/or methacrylates, mixtures of the stated lactone
adducts with the above hydroxyalkyl acrylates and/or methacrylates
in any desired ratio from 1:99 to 99:1. The unsaturated lactone
adducts are prepared by a conventional method, as described in
German Laid-Open application DOS No. 3,027,776, for example by
reacting hydroxyl-containing acrylates and/or methacrylates with
.epsilon.-caprolactone, the ratio of the number of equivalents
being from 1.5:1 to 1:3; the reaction is carried out at from 60 to
130.degree. C. in the presence of from 0.01 to 0.15% by weight of
an organotin catalyst, eg. dibutyl-tin oxide or dibutyl-tin
diacetate, while passing air through the mixture.
The copolymer (A) used according to the invention contains from 6
to 70, preferably from 6 to 50, % by weight of component (a) as
copolymerized units.
(b) Examples of suitable hydroxyalkyl esters of acrylic acid and/or
methacrylic acid of the general formula ##STR11## where R is
hydrogen or methyl and R'" is the alkyl radical of a branched
carboxylic acid of 4 to 26 carbon atoms, are
trimethylacetoxyglycidyl (meth)acrylate and versatic acid glycidyl
ester acrylate and methacrylate. Mixtures of the stated
hydroxyalkyl methacrylates and acrylates are also suitable.
The polyhydroxypolyacrylate resin (A) can contain from 0 to 50,
preferably from 0 to 25, % by weight of component (b) as
copolymerized units. The sum of the percentages stated under (a)
and (b) is from 6 to 70, preferably from 6 to 50, % by weight.
(c) Examples of suitable alkyl esters of acrylic acid and/or
methacrylic acid which form homopolymers having a glass transition
temperature of from +5 to +120.degree. C. are methyl acrylate,
methyl methacrylate, ethyl methacrylate, tert.-butyl acrylate,
n-butyl methacrylate and i-butyl methacrylate as well as mixtures
of these, methyl methacrylate and tert.-butyl acrylate being
preferred.
The copolymer (A) used according to the invention contains from 10
to 50, preferably from 25 to 50, % by weight of component (c) as
copolymerized units. (d) Examples of suitable vinylaromatics are
styrene, .alpha.-methylstyrene, o-- and p-chlorostyrene, o--, m--
and p--, methylstyrene and p-tert.-butylstyrene as well as mixtures
of these, styrene being preferred.
The polyhydroxypolyacrylate resin (A) can contain from 0 to 10,
preferably from 0 to 7, % by weight of the vinylaromatics (d) as
copolymerized units.
The sum of the percentages stated under (c) and (d) is in general
from 10 to 50, preferably from 25 to 50, by weight.
(e) Examples of suitable alkyl esters and/or alkylglycol esters of
acrylic acid and/or methacrylic acid, where the esters form
homopolymers having a glass transition temperature of from
-80.degree. to +4.5.degree. C. and their alkylglycol esters contain
not more than 2 ether oxygen bridges, are ethyl acrylate, n-butyl
acrylate, i-butyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl
methacrylate, ethylglycol acrylate, ethylglycol methacrylate,
ethyldiglycol acrylate, ethyldiglycol methacrylate, lauryl acrylate
and lauryl methacrylate as well as mixtures of these, n-butyl
acrylate and i-butyl acrylate being preferred.
The copolymer (A) used according to the invention contains from 10
to 60, preferably from 20 to 50, % by weight of component (e) as
copolymerized units.
(f) Examples of suitable acrylamides and/or methacrylamides which
may or may not be substituted at the amide nitrogen by one or two
alkyl radicals of 1 to 8 carbon atoms which may or may not contain
a carbonyl group, or by one or two phenyl radicals are acrylamide,
methacrylamide, N-methylacrylamide, N-methylmethacrylamide,
N-ethylacrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide,
N,N-diethylacrylamide, N,N-diisopropylacrylamide,
N-phenylacrylamide, N,N-di-n-butylacrylamide and
N-(1,1-dimethyl-3-oxobutyl)-acrylamide (diacetoneacrylamide),
acrylamide and methacrylamide being preferred.
The polyhydroxypolyacrylate resin (A) can contain from 0 to 10,
preferably from 0 to 5, % by weight of component (f) as
copolymerized units.
(g) Examples of suitable polymerizable olefinically unsaturated
heterocyclic compounds of the above general formulae (I) to (VIII),
where R is hydrogen or methyl, R.sup.1, R.sup.2, R.sup.3 and
R.sup.4 are identical or different and are each hydrogen, methyl,
ethyl, a straight-chain or branched alkyl radical of 3 or 4 carbon
atoms, or phenyl which is unsubstituted or substituted by alkyl of
1 to 4 carbon atoms, halogen, eg. chlorine or bromine, nitro, or
are each a group of the general formula --R.sup.I --A--R.sup.II,
where A is oxygen or sulfur, R.sup.I is methylene or ethylene or is
phenylene which is unsubstituted or substituted by alkyl of 1 to 4
carbon atoms or by halogen or nitro and R.sup.II is methyl or ethyl
or is phenyl which is unsubstituted or substituted by alkyl of 1 to
4 carbon atoms or by halogen or nitro, or are each halogen or
nitro, or a group of the general formulae --OR.sup.III,
--COOR.sup.III, --SO.sub.2 R.sup.III, --CONR.sup.III R.sup.IV or
--SO.sub.2 NR.sup.III.sub.R.sup.IV, where R.sup.III and R.sup.IV
are identical or different and are each methyl, ethyl, a
straight-chain or branched alkyl radical of 3 or 4 carbon atoms, or
phenyl which is unsubstituted or substituted by alkyl of 1 to 4
carbon atoms or by halogen or nitro, and furthermore in the
formulae (I), (II), (III), (V), (VI) and (VIII) R2 and R.sup.3, or
in the formula (III) R.sup.3 and R.sup.4, or in the formulae (II)
and (IV) R.sup.3 and R.sup.4 or R.sup.1 and R.sup.2, or in the
formulae (II) and (IV) R.sup.3 and R.sup.4 and R.sup.1 and R.sup.2,
together with the heterocyclic ring, can form a fused aromatic
six-membered ring which is unsubstituted or substituted by alkyl of
1 to 4 carbon atoms or by halogen, eg. chlorine or bromine, or
nitro, are N-vinylimidazoles, such as 1-vinyl-2-methylimidazole,
1-vinyl-2-phenylimidazole, 1-vinylbenzimidazole,
1-vinyl-2-ethylimidazole, 1-propenyl-2-methylimidazole,
1-vinyl-4-methylimidazole, 1-vinyl-2-ethyl-4-methylimidazole,
1-vinyl-4-nitroimidazole, 1-vinylimidazole and 1-propenylimidazole
as well as mixtures of these, 1-vinylimidazole,
1-vinyl-2-methylimidazole and 1-vinyl-2-phenylimidazole being
preferred. Other suitable olefinically unsaturated heterocyclic
compounds (g) are vinylheterocyclic compounds of the formulae (II)
to (VIII), eg. 2-vjnylpyridine, 3-vinylpyridine, 4vinylpyridine,
5-ethyl-2-vinylpyridine, 6-methyl-3-vinylpyridine,
2-vinylquinoline, 2-vinylisoquinoline, 4-vinylquinoline,
2-vinylquinoxaline, 4-vinylquinazoline, 2-vinylpyrimidine,
4-vinylpyrimidine and 2-vinylpyridazine as well as mixtures of
these, 3-vinylpyridine and 4-vinylpyridine being preferred.
The copolymer (A) used according to the invention contains from 1
to 25, preferably from 2 to 20, % by weight of component (g) as
copolymerized units.
(h) Examples of suitable monomers not mentioned under (a) to (g),
whose copolymerized radicals are inert to isocyanate groups, ie. do
not react with isocyanate or blocked isocyanate groups under the
reaction conditions employed in the novel process, are vinylesters
of carboxylic acids of 1 to 12 carbon atoms, eg. vinyl acetate,
vinyl propionate, vinyl pivalate, vinyl 2-ethylhexanoate, vinyl
laurate or vinyl benzoate, vinyl halides, eg. vinyl chloride,
vinylidene halides, eg. vinylidene chloride, and N-vinylpyrrolidone
and N-vinylcaprolactam, as well as mixtures of the stated
monomers.
The polyhydroxypolyacrylate resin can contain from 0 to 20,
preferably from 0 to 10, % by weight of component (h) as
copolymerized units.
The sum of the percentages stated under (a) to (h) is 100.
The hydroxyl-containing copolymer (A) has a hydroxyl number of in
general from 30 to 250, preferably from 50 to 150.
The polyhydroxypolyacrylate resin (A) can be prepared from the
monomers (a) to (h) by a conventional polymerization process, for
example by continuous or batchwise free radical polymerization,
preferably by a batchwise procedure in organic solution at from
80.degree. to 160.degree. , for example in the presence of a free
radical initiator. The polyhydroxypolyacrylate resins (A) generally
have number average mean molecular weights (M.sub.n) of from 1,000
to 20,000, preferably from 2,000 to 10,000, or K values (according
to Fikentscher) of from 12 to 40, preferably from 15 to 30, and,
for the novel process, are advantageously employed in solution in
an organic solvent which is inert to isocyanate groups. Examples of
suitable solvents of this type are esters, such as n-butyl,
acetate, ethyl acetate or isopropyl acetate, ethers, such as
tetrahydrofuran, dioxane or diethylglycol, ethyl-esters, such as
ethyl glycol acetate, methyl glycol acetate and butyl glycol
acetate, hydrocarbons, in particular aromatic hydrocarbons, such as
xylene, toluene or ethylbenzene, and halohydrocarbons, such as
chlorobenzene, as well as mixtures of these.
(B) Suitable isocyanurate-containing polyisocyanates which may or
may not contain biuret groups, are unblocked or partially or
completely blocked with CH--, NH--or OH--acidic blocking agents,
have a functionality of from 2.5 to 6, preferably from 3 to 5, and
are used according to the invention are those which posses
predominantly cycloaliphatically bonded isocyanate groups. Examples
of suitable polyisocyanates for this purposed are polyisocyanate
mixtures (B) whose principal component (B1) is preferably an
isocyanurate-containing trimer of 3-isophorone diisocyanate, IPDI).
The preparation of such isocyanurate-containing polyisocyanates can
be carried out, for example, by a conventional method, as described
in, for example, British Pat. No. 1,391,066 or German
Laid-Open application Nos. DOS 2,325,826 or DOS 2,732,662, for
example by trimerization of the diisocyanate at from about
40.degree. to 120.degree. C. in the presence of a catalyst, for
example a metal compound, e.g. a metal naphthenate, an alkaline
earth metal acetate, formate or carbonate, a metal alkoxide or iron
acetylacetonate, preferably secondary and tertiary amines, such as
aziridines in combination with trialkylamines or
triethylenediamine, combined with propylene oxide.
Isocyanurate-containing polyisocyanates based on
1,4-diisocyanatocyclohexane (cyclohexane 1,4-diisocyanate) and
4,4'-diisocyanatodicyclohexylmethane (dicyclohexylmethane
4,4'-diisocyanate) are also suitable.
Examples of isocyanate components (B2) used for the novel process
are isocyanate adducts which contain biuret groups and
predominantly aliphatically bonded isocyanate groups.
A particularly preferred compound of this type is biuretized
hexamethylene diisocyanate, which has long been known and, as
stated above, is used specifically in two-component polyurethane
surface coatings for the automotive repair sector. It is prepared,
as described in, for example, German Patent Nos. 1,101,394,
1,104,394, 1,174,759, 1,174,760, 1,227,004 and 1,227,007, British
Patent No. 1,044,932 and German Laid-Open application No. DOS
1,931,055, for example by the action of free or bonded water (for
example in the form of water of crystallization or in the form of
formic acid), primary aliphatic monoamines or tertiary aliphatic
monoalcohols on hexamethylene diisocyanate at from 80.degree. to
200.degree. C., followed by the removal of the excess diisocyanate
by distillation under reduced pressure in a thin-film evaporator.
Other isocyanate components (B2) which can be used according to the
invention are isocyanurate-containing polyisocyanates trimerization
of some of the isocyanate groups of organic diisocyanates, as
described in, for example, German Patent No. 1,201,992, and German
Laid-Open application Nos. DOS 1,644,809, DOS 1,670,667, DOS
2,325,826, DOS 2,616,415, DOS 2,616,416, DOS 2,644,684, DOS
2,724,914 and DOS 2,806,731.
The isocyanate mixture (B) consists of from 60 to 99, preferably
from 70 to 99, % by weight of polyisocyanates (B1) which possess
isocyanurate groups and predominantly cycloaliphatically bonded
isocyanate groups, and from 1 to 40, preferably from 1 to 30, % by
weight of the last-mentioned polyisocyanates (B2) which contain
biuret and/or isocyanurate groups and possess predominantly
aliphatically bonded isocyanate groups, the sum of the percentages
stated under (B1) and (B2) being 100.
Instead of the above mixtures of the polyisocyanate components (B1)
and (B2), the novel process can also be carried out using
isocyanurate-containing polyisocyanates (B) which possess
predominantly cycloaliphatically bonded isocyanate groups and
contain both cycloaliphatic and aliphatic diisocyanates as
copolymerized units. Examples of suitable cycloaliphatic
diisocyanates are 1,4-diisocyanatocyclohexane and
4,4'-diisocyanatodicyclohexylmethane, but preferably isophorone
diisocyanate, while the preferred aliphatic diisocyanate is
hexamethylene diisocyanate. These mixed cycloaliphatic/aliphatic
polyisocyanates can be prepared, as described in German Laid-Open
application No. DOS 3,033,860, by trimerization of the diisocyanate
mixture at from 40.degree. to 100.degree. C., preferably using a
suitable hydroxyl-substituted quaternary ammonium hydroxide. Mixed
isocyanurate-containing adducts which are suitable for the novel
process contain, as copolymerized units, for example (1) from 60 to
99 preferably from 70 to 98, % by weight of a cycloaliphatic
diisocyanate, preferably isophorone diisocyanate, and 2) from 1 to
40, preferably from 2 to 30,% by weight of an aliphatic
diisocyanate, preferably hexamethylene diisocyanate, the sum of the
percentages stated under ( 1) and (2) being 100.
Of course, the novel process can be carried out using any of the
above polyisocyanate adducts in any possible combination.
The use, according to the invention, of such polyisocyanate
mixtures which comprise minor amounts of adducts which contain
biuret groups and aliphatically bonded isocyanate groups (for
example compounds based on hexamethylene diisocyanate) or trimers
obtained from cycloaliphatic diisocyanates and minor amounts of
aliphatic diisocyanates (for example isophorone diisocyanate and
hexamethylene diisocyanate) has the following advantages over the
prior art: on the one hand, the use of even relatively small
amounts of aliphatic isocyanate adducts results in surface coating
films which possess excellent flexibility and undergo crosslinking
rapidly; on the other hand, surprisingly, the advantages implicit
in the use of cycloaliphatic trimers, for example very hard
coatings, a relatively advantageous pot life and in particular low
toxicity of the inhaled surface coating mixtures, are substantially
retained.
Suitable blocking agents for the surface coating polyisocyanates
(B) are: CH--, NH--or OH--acidic blocking agents, e.g. dialkyl
malonates, dialkyl acetoacetates, acetylacetone,
.epsilon.-caprolactam, pyrrolidone, phenols, p-hydroxybenzoates,
cyclohexanol, t-butanol and preferably oximes, such as benzophenone
oxime, cyclohexanone oxime, methyl ethyl ketoxime or dimethyl
ketoxime. Monofunctional ketoximes, in particular methyl ethyl
ketoxime and dimethyl ketoxime, are particularly preferred.
Component (B) can be unblocked or partially or completely blocked,
but unblocked polyisocyanates are preferred. ferred.
The ratio of the two binder components used according to the
invention, i.e. of the polyisocyanate (B) to the
polyhydroxypolyacrylate (A) is advantageously chosen so that the
ratio of the number of equivalents of isocyanate groups (blocked or
unblocked) to reactive hydroxyl groups is from 0.25 : 1 to 4 : 1,
preferably from 0.5 : 1 to 2 : 1.
Coatings are produced by the novel process by mixing components (A)
and (B), advantageously dissolved in an organic solvent or solvent
mixture, if necessary adding pigments, such as conventional white
and black pigments, e.g. titanium dioxides (rutile), zinc sulfides
or carbon black, or colored pigments, e.g. cadmium sulfide, iron
oxide yellow, iron oxide red, chromium oxide, benzidine yellow,
phthalocyanine blue, phthalocyanine green, thioindigo or
quinacridones, for example in amounts of not more than 250%, based
on the total amount of binder (components (A) and (B)), as well as
other assistants and additives conventionally used for processing
two-component surface coatings, and then applying the mixture onto
the substrate to be coated. In principle, catalysts, such as metal
compounds, e.g. lead naphthenate, zinc naphthenate, cobalt
naphthenate, lead octoate, tin octoate, calcium octoates
dibutyl-tin diacetate, dibutyl-tin dilaurate or iron
acetylacetonate, and bases, such as triethylenediamine or
diethylethanolamine, can also be used, in amounts of about
0.001-10% by weight, based on the total amount of binder, but the
coatings are preferably produced without the addition of a catalyst
since, as stated above, a surprising advantage of the novel surface
coating mixtures is that they harden very rapidly in the absence of
an accelerator to give hard, scratch-resistant coatings resistant
to premium grade gasoline but still have a pot life which meets
practical requirements.
Suitable methods of application are the conventional ones, for
example spraying, dipping, painting or roller-coating.
The novel process can be used for coating, for example, metal
components made of aluminum, zinc, tin, iron or steel, e.g. steel
sheet, or galvanized steel sheet or aluminum sheet, as well as
other substrates, such as wood, paper, concrete or plastics, e.g.
PVC or nylon.
After application onto the substrate, the coatings can be cured in
a conventional manner, for example at room temperature in the
course of from 24 hours to 7 days; advantageously, drying in the
air is carried out at room temperature, followed by curing at about
60.degree.-80.degree. C. in the course of from 20 to 60
minutes.
The process according to the invention can be used to produce
coatings which have particularly advantageous properties. The
coatings obtained according to the invention are distinguished in
particular by high scratch-resistance, excellent resistance to
premium grade gasoline after relatively short drying times, high
flexibility, high gloss and excellent weather-resistance coupled
with rapid curing, and the surface coating mixtures from which the
coatings are produced have relatively long pot lives.
In the Examples and Comparative Examples, parts and percentages are
by weight, unless stated otherwise.
Preparation of the polyhydroxypolyacrylate resins
The polyhydroxypolyacrylate resins A to G are prepared by a prior
art method.
Polyacrylate resin A
100 parts of a 1:1 mixture of n-butyl acetate and xylene are heated
at 100.degree. C. in a reaction vessel provided with a paddle
stirrer, a reflux condenser, a feed vessel, a thermometer and a gas
inlet tube. A solution of 77.5 parts of butane-1,4-diol
monoacrylate, 42.5 parts of hydroxyethyl acrylate, 75 parts of
methyl methacrylate, 90 parts of t-butyl acrylate, 190 parts of
n-butyl acrylate, 25 parts of 1-vinylimidazole and 10 parts of
azodiisobutyronitrile in 130 parts of a 1:1 mixture of n-butyl
acetate and xylene is added dropwise in the course of 4 hours at a
constant rate and in the absence of air (in a gentle stream of
nitrogen), while maintaining the temperature of 100.degree. C. and
stirring vigorously. Further polymerization is then carried out by
uniformly metering 2.5 parts of azodiisobutyronitrile in 75 parts
of a 1:1 mixture of n-butyl acetate and xylene in the course of 2
hours.
The resulting polyacrylate resin has the following
characteristics:
Hydroxyl number=about 102 (based on solids)
Viscosity at 23.degree. C.=2750 mPa.s
K value (3% strength in dimethylformamide)=21.8.
Polyacrylate resins B to D and F to G
The preparation of the copolymers is carried out as described for
polyacrylate resin A. The composition and characteristics of the
products are shown in Table 1.
TABLE 1
__________________________________________________________________________
6 Polyacrylate resin B C D F G
__________________________________________________________________________
Butane-1,4-diol monoacrylate (parts) -- -- -- 38.5 -- Hydroxyethyl
acrylate (HEA) (parts) 103 103 103 -- 31 Adduct of HEA and
.SIGMA.--caprolactone* (parts) -- -- -- 143.5 143.5 Methyl
methacrylate (parts) 100 50 50 75 100 Styrene (parts) -- 40 65 --
-- t-Butyl acrylate (parts) 125 150 150 153 153 n-Butyl acrylate
(parts) 147 132 132 65 72.5 1-Vinylimidazole (parts) 25 25 -- 25 --
Hydroxyl number (mg of KOH/g, about about about about about based
on solids) 98 100 98 100 100 Viscosity at 23.degree. C. (mPa.s)
3,100 3,450 3,050 3,900 3,500 K value (3% strength in 22.0 23.4
22.5 22.9 22.7 dimethylformamide)
__________________________________________________________________________
*prepared from 50.4% by weight of hydroxyethyl acrylate and 49.6%
by weight of .SIGMA.--caprolactone; molar ratio 1:1
Polyacrylate resin E
A mixture of 100 parts of ethylglycol acetate, 200 parts of xylene
and 149 parts of glycidyl esters of .alpha.,
.beta.-dialkylalkanemonocarboxylic acids of the empirical formula
C.sub.13 H.sub.24 O.sub.3 is heated at 135.degree. C. in a reaction
vessel as described above. A mixture of 101 parts of methyl
methacrylate, 94 parts of hydroxyethyl methacrylate, 111 parts of
styrene, 44 parts of acrylic acid, 1.5 parts of t-dodecylmercaptan
and 5 parts of di-tert.-butyl peroxide is then added dropwise at a
constant rate in the course of 2 hours at this temperature, and the
resin solution is left to continue reacting for a further 6 hours
at 135.degree. C. The polymer solution has a solids content of 60%,
which is brought to 50 % with xylene; the solution has an efflux
time of 250 sec in DIN cup 4 at 23.degree. C. Further
characteristics are as follows:
OH number (based on solids)=150
Acid number=7
K value=23.9
Polyisocyanates used
The following polyisocyanate components (B) are employed for the
preparation of the novel coatings:
Polyisocyanate I
An isocyanurate-containing polyisocyanate which possesses
predominantly cycloaliphatically bonded isocyanate groups, is based
on isophorone diisocyanate and has an NCO content of about 12%;
used as a 70% strength solution in a 1:1 mixture of xylene and
ethyleneglycol acetate.
Polyisocyanate II
A polyisocyanate which contains biuret groups and aliphatically
bonded isocyanate groups, is based on hexamethylene diisocyanate
and has an NCO content of about 16.5%; used as a 75% strength
solution in a 1:1 mixture of xylene and ethylglycol acetate.
Polyisocyanate III
An isocyanurate-containing polyisocyanate which contains
aliphatically bonded isocyanate groups, is based on hexamethylene
diisocyanate and has an NCO content of about 22%; used without a
solvent.
1. Testing unpigmented two-component reactive surface coatings
The above polyacrylate resins A to G are combined with the mixtures
of polyisocyanates I to III, as shown in Table 2, and the
properties of the resulting clear surface coating films are
determined.
To do this, 500 parts, in each case, of copolymer solutions, having
a solids content of about 62% for Examples 1 to 9 and Comparative
Examples 10, 11, 14 and 15 and about 50% for Comparative Examples
11 and 12, are mixed carefully with the stoichiometric amounts,
stated in Table 2, of the polyisocyanate components I to III, and
the mixture is then diluted to spray viscosity (efflux time 20 sec,
DIN cup 4 at 23.degree. C.) with n-butyl acetate. In addition, in
the case of Comparative Examples 10, 12 and 14, one formulation is
prepared in each case with the addition of a catalyst (30 parts of
a 1% strength solution of dibutyl tin dilaurate in n-butyl acetate,
corresponding to 0.07%, based on solids, and 46 parts of a 4%
strength solution of calcium octoate in n-butyl acetate,
corresponding to 0.43%, based on solids). The mixtures are then
sprayed onto steel sheets to give a film which is from 40 to 50
.mu.m thick when dry. The surface coating films are either cured
for 1 day and 7 days at room temperature or are first dried in the
air for 30 minutes at room temperature and then cured in a
through-circulation drier for 30 minutes and 60 minutes, at
80.degree. C. in each case. The Konig pendulum hardness, the
scratch-resistance and the Erichsen deep-drawing value are
determined for the coatings cured for 7 days at room temperature
and for 60 minutes at 80.degree. C., the Konig pendulum hardness is
determined for the coating cured for 1 day at room temperature, and
the pendulum hardness and the Erichsen deep-drawing value are
determined for the coating cured for 30 minutes at 80.degree. C.
The test results are summarized in Table 2.
As Table 2 shows, the clear surface coating films prepared
according to the invention and without the use of a catalyst
simultaneously exhibit rapid curing, great final hardness,
scratch-resistance and flexibility both when dried at room
temperature and when drying is forced. The films (cf. Comparative
Examples 10 to 15) correspondingly obtained from prior art
polyacrylate resins and a mixture of isocyanurate-containing
polyisocyanate based on isophorone diisocyanate (polyisocyanate I)
with a biuret-containing polyisocyanate based on hexamethylene
diisocyanate (polyisocyanate II) exhibit a much less advantageous
spectrum of properties than the novel coatings, even when large
amounts of catalyst are used. For example, either the films are
very flexible but harden relatively slowly and possess only
moderate final hardness and scratch-resistance, or they possess
improved hardness and scratch-resistance but in some cases are not
sufficiently flexible.
TABLE 2
__________________________________________________________________________
Clear surface coating mixtures Properties of the white surface
coating films Exam- Acrylic Polyisocyanate Curing at room
temperature Curing at 80.degree. C. ple resin (parts) 1 day 7 days
30 min 60 min No.* solution I II III PH (sec) PH (sec) SR ED (mm)
PH (sec) SR ED (mm) PH (sec) SR ED
__________________________________________________________________________
(mm) 1 A 173 18 134 170 1 8.4 197 0-1 8.2 197 0 7.5 2 A 150 35 133
168 0 8.1 196 0 8.0 196 0 7.7 3 A 127 51 147 165 1 8.5 190 1 8.3
192 0-1 8.2 4 A 150 26 137 173 0-1 8.6 195 0-1 8.3 198 0 7.8 5 B
144 34 125 176 0 9.1 199 0 9.0 199 0 8.9 6 B 144 25 130 178 0-1 9.0
202 1 9.1 199 0 8.6 7 C 147 34 127 178 0-1 9.2 200 0-1 9.1 203 0
9.2 8 C 147 25 133 181 1 9.1 203 1 9.2 202 0-1 8.7 9 F 147 34 120
175 0 10.2 198 0 10.5 205 0 9.0 10 D 144 34 31 112 3 9.8 115 3 10.0
136 2-3 6.3 11 as for 10; but with the: 103 152 2 4.5 145 2-3 5.0
170 1 2.3 addition of a catalyst** 12 E 178 42 95 185 1 1 203 1 1
200 1 2.3 13 as for 12; but with the: 130 195 0 1 197 0 1.3 205 0
5.0 addition of a catalyst** 14 G 147 34 93 160 2-3 3.4 155 2-3 4.0
178 1-2 6.5 15 as for 14; but with the: 112 165 1-2 5.8 172 1-2 6.8
180 0 6.0 addition of a catalyst**
__________________________________________________________________________
*Examples 10 to 15 are Comparative Examples **Catalyzed with 30
parts of a 1% strength solution of dibutyltin dilaurate in nbutyl
acetate/46 parts of a 4% strength solution of calcium octoate in
nbutyl acetate Abbreviations: PH: Konig pendulum hardness (sec)
according to DIN 53,157 SR: Scratchresistance, rating 05, according
to DIN 53,230 ED: Erichsen deepdrawing value (mm), according to DIN
53,156
2. Testing the pigmented two-component reactive surface coatings
(corresponding to Examples 1 to 9 and Comparative Examples 10 to
15)
500 parts of the copolymer solutions, having a solids content of
about 62% in the case of Examples 1 to 9 and Comparative Examples
10, 11, 14 and 15, and of about 50% in the case of Comparative
Examples 12 and 13, are milled with 440 parts of titanium dioxide
(rutile) and 150 parts of a 4:4:2 solvent mixture of n-butyl
acetate, xylene and ethyl glycol acetate to give a surface coating
mixture. In each case, the stoichiometric amount, stated in Table
2, of polyisocyanate mixture is added to the pigmented surface
coating mixture, and the surface coating mixture obtained is
diluted to spray viscosity (efflux time 20 sec, DIN cup 4 at
23.degree. C.) with the solvent mixture stated above. In addition,
in the case of Comparative Examples 11, 13 and 15, a formulation is
prepared in each case with the addition of a catalyst mixture
comprising 30 parts of a 1% strength solution of dibutyl-tin
dilaurate (corresponding to 0.07% solids, based on the binder) and
46 parts of a 4% strength solution of calcium octoate in n-butyl
acetate (corresponding to 0.43% solids, based on binder). The
surface coatings are then sprayed onto steel sheets to give a film
which is about 50 .mu.m thick when dry. The coated sheets are dried
in the air for 30 minutes at room temperature and then dried in a
through-circulation drier for 60 minutes at 80.degree. C.;
furthermore drying is carried out of 7 days at room temperature. In
each case, the Konig pendulum hardness according to DIN 53,157, the
scratch-resistance according to DIN 53,230, the Erichsen
deep-drawing value according to DIN 53,156 and the resistance to
premium grade gasoline are determined for the hardened surface
coating film (in each case after drying for 60 minutes at
80.degree. C. and after drying for 4 days at room temperature);
furthermore, the pot life of the ready-prepared surface coating
mixtures is determined, this being the time which elapses before
the solutions which have been brought to spray viscosity undergo
gelling at 23.degree. C.
TABLE 3
__________________________________________________________________________
Properties of the white surface coating films pot Curing at room
temperature Example life** Curing for 60 minutes at 80.degree. C. 7
days GR No.* (h) PH (sec) SR ED (mm) GR PH (sec) SR ED (mm) (after
4 days)
__________________________________________________________________________
1 23 157 0 7.2 0 145 0 7.5 0 2 22 153 0-1 8.0 0-1 140 0-1 8.0 0 3
18 153 0-1 8.5 0 138 0-1 9.2 0 4 25 158 0 7.8 0-1 140 0-1 8.3 0-1 5
25 158 0-1 7.9 0 145 0 8.0 0-1 6 26 162 0 8.4 0 135 0 7.8 0-1 7 23
160 0 8.0 0 143 0 8.2 1 8 22 165 0 7.7 0 150 0 7.5 0-1 9 23 157 0
8.6 0 145 0 9.6 0 10 >50 90 3 10.4 5 65 3 10.5 5 11 5 153 1 4.8
1-2 115 3 8.5 3-4 12 45 164 0 2.9 0-1 148 0 1 1 13 20 158 0 3.8 0
151 0 1 0-1 14 50 131 2 8.9 3-4 135 2 8.3 3-4 15 7 155 1 5.8 2 161
1 6.0 2-3
__________________________________________________________________________
*Examples 10 to 15 are Comparative Examples **Time in hours until
gelling of the surface coatings at spray viscosity (an efflux time
of about 20 sec in DIN cup 4 at 23.degree. C.) Abbreviations: PH:
Konig pendulum hardness (sec), according to DIN 53,157 SR:
Scratchresistance, rating 0-5, according to DIN 53,230 ED: Erichsen
deepdrawing value (mm), according to DIN 53,156 GR: Resistance to
premium grade gasoline
To test the resistance to premium grade gasoline, a ball of
cottonwool impregnated with premium grade gasoline is allowed to
act on the hardened surface coating film for 5 minutes, the
cottonwool ball being covered with a glass dish during this time.
The cottonwool ball is removed and the coating is then dried in the
air for 35 minutes, after which evaluation is carried out (rating
from 0 to 5, according to DIN 53,230).
The test results are summarized in Table 3. The pigmented surface
coatings of Examples 1 to 9 and of Comparative Examples 10 to 15
give highly glossy smooth surface coating films. Table 3 shows
clearly that the novel surface coating mixtures without added
catalyst harden very rapidly to give very flexible, hard,
scratch-resistant films having excellent resistance to premium
grade gasoline, and at the same time possess pot lives which
conform to processing requirements. Although the surface coatings
obtained in Comparative Example 10 are very flexible, they do not
possess adequate hardness, scratch-resistance and resistance to
premium grade gasoline. The addition of large amounts of catalyst
to the corresponding surface coating results in films which possess
adequate hardness and flexibility but which in some cases are not
sufficiently scratch-resistant and gasoline-resistant; the pot life
(5 hours) of the resulting surface coating mixture no longer
conforms to processing requirements (cf. Comparative Example 11).
The films of Comparative Examples 12 and 13, obtained,
respectively, without and with a catalyst, possess good final
hardness, scratch-resistance and resistance to premium grade
gasoline on the one hand, and completely inadequate flexibility on
the other hand. Comparative Example 14 gives films which are
sufficiently hard and very flexible but which possess only moderate
scratch-resistance and inadequate gasoline-resistance, while the
catalyzed formulation (Comparative Example 15) has much too short a
pot life and gives films which are also not sufficiently resistant
to premium grade gasoline.
* * * * *